Conventional wisdom agrees that industrial pollution, carbon dioxide emissions and an increased use of fossil fuels are directly contributing to a global warming trend. You've heard about it at school, at work, on the news -- even in sitcoms. Former U.S. Vice President Al Gore won an Academy Award and a Nobel Prize for his documentary on climate change, "An Inconvenient Truth." This warming trend is expected to result in glacial melting, rising sea levels, droughts, increased severe weather events like tornadoes and hurricanes, species extinctions, and a harder life in general for humanity.

Some people feel that the harsh effect of climate change on humankind is poetic punishment for crimes against the Earth. After all, everybody knows that climate change is humanity's fault. Right? Global warming proponents and skeptics are deeply divided, angrily attacking each other as crackpots who dismiss the obvious effects of global warming or sheep-like followers who have bought into environmental chicanery.

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­The United Nations founded the Intergovernmental Panel on Climate Change (IPCC) in 1988 as a think tank for thousands of scientists covering a wide array of specialties, all working together to examine global warming and what can be done to circumvent it. Over two decades, the panel became the leading authority on climate change and its study, producing reports that form the definitive source of information on global warming. Climate skeptics single out the work of this body in their search for logical flaws.

But finding flaws works both ways. The environmental organization Greenpeace discredited many climate skeptic groups by exposing companies with a vested interest in disavowing global warming -- like oil conglomerate Exxon-Mobil -- as major sources of funding for these groups. Greenpeace claims its efforts -- like the ExxonSecrets project -- had the effect of Exxon cutting off funding to some of these groups [source: ExxonSecrets].

Everyday people on both sides of the debate are also doing more to follow their beliefs. On the extreme end, at least two women underwent sterilization procedures because they believe that having children will only serve to worsen the population growth problems facing the Earth [source: Fox News].

On the other side, two Russian solar physicists made a $10,000 bet with a British climatologist that the Earth will actually cool in the next decade. These physicists believe that we are merely experiencing a temporary climate shift based on solar fluctuations, which will return to normal in the next few years. They're basing their bet on comparisons between global surface temperatures taken between 1998 and 2003 with ones that will be taken from 2012 to 2017 [source: Adam].

It's evident the debate over climate change is a heated one. Are skeptics clouding the public judgment for money? Are climate-change believers merely alarmists who risk the present for the future? It's wise to remember that for each argument one side makes, the other has a counterargument and can dismiss th­e other every step of the way.

While the public is well-versed in arguments for human-induced climate change, let's examine what some skeptics believe. Read the next page to find out what the other side thinks.

Global Warming Skeptics' Arguments

Weather stations like this one collect information throughout the world. But are some more reliable than others?

Since global warming became a major issue, climatology has become a hot-button scientific field. Weather stations throughout the world collect data to help scientists create computer models that help them track global climate change.

Some people simply don't believe that the Earth is undergoing a global warming trend or climate change. Others believe in global warming and climate change, but don't believe that people are responsible. The skeptics who don't believe in global warming at all are the ones who most vehemently attack weather data, the analysis of the climatologists and the predictions of the models.

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Anti-global warming skeptics say the placement of some weather stations in urban areas may produce inaccurate measurements. According to them, the data are being corrupted by the urban heat island, an effect produced by cities' transportation, large amounts of heat-absorbing asphalt, and high concentrations of carbon dioxide coming from the many homes and businesses in high-population areas.

Global warming skeptics also believe the models used to predict Earth's future under global warming are unreliable. They feel that while the sun, clouds, gases, glaciers and oceans are responsible for weather, so, too, are other factors, including some we don't currently understand. According to global warming skeptics, computer models are merely a guess at what will happen on Earth in the future -- something climatologists don't deny -- and an arguably poor guess at that. After all, if we can't accurately predict the weather a week from now, how can we predict the global climate in 100 years?

Others don't believe we're experiencing a global warming trend at all. The annual temperature between 1998 and 2007 actually decreased, despite the 4 percent increase in carbon dioxide in the atmosphere during that same period. They also point out that, while the Northern Hemisphere has warmed, the Southern Hemisphere has actually cooled. "Global warming was supposed to actually be global, not hemispheric," says skeptic -- and Executive Director of the Natural Resources Stewardship Project -- Tom Harris [source: Canada Free Press].

These same skeptics find fault in the historical data used to graph things like glacial loss and hurricane frequency. Although weather data, like temperature, have been actively collected since 1850, it wasn't until the relatively recent access to detailed weather satellite photography that scientists were able to see changes in the Greenland ice shelf that global warming believers say is in such danger. Skeptics ask: How can we know how long it's been receding?

Perhaps the meteorological event most often used by global warming skeptics as a counterargument is the Medieval Warm Period. Around the 9th to 14th centuries, regions around the world experienced an increase in temperatures, similar to what we see today [source: National Oceanic and Atmospheric Administration]. Following this period, the Earth experienced a Little Ice Age where global temperatures cooled. It is conceivable that the Earth is currently experiencing something similar to this, skeptics say. Their point is, we simply don't know enough about long-term weather systems to say for certain one way or the other.

The skeptics of human-caused (anthropogenic) global warming don't dismiss global warming outright, they just don't believe that human activity is responsible. Learn more about their beliefs on the next page.

Anthropogenic Skeptics

Ice core samples, like this one collected in Antarctica in 1993, are used to support and disprove theories about climate change.

A 2003 research paper published in the journal Science discussed the analysis of three ice core samples taken from Antarctica. The ice was around 240,000 years old, from the third Termination period, a climactic shift which ends each ice age. The findings showed that carbon dioxide concentrations rose between 600 to 1000 years before temperatures did, and before the Antarctic glaciers began to melt. The paper's authors suggested that carbon dioxide may not be the cause of global warming, but that it contributes to the process: Rising temperatures release carbon dioxide trapped in glacial ice and elsewhere, causing global temperature to rise even further.

This paper shows that the carbon dioxide increases may follow rising temperatures, not the other way around. What's more, the ice samples suggest this is a natural process. This observation is just one of the factors that, in the eyes of anthropogenic global warming skeptics, lets humans off the hook for global warming. Although they are satisfied with findings that the Earth is in a major warming trend, anthropogenic global warming skeptics believe that science places the blame on humanity without enough scientific proof to back it up.

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Skeptics of anthropogenic climate change claim that reports compiled by the Intergovernmental Panel on Climate Change are the result of diplomatic negotiations, rather than unbiased science. For example, a representative from an oil-producing state may object to including analysis which is particularly harsh toward use of fossil fuels in a report. If all of the science isn't present in the reports released by the IPCC, skeptics reason, what else is missing?

For example, in 2001, the IPCC used a graph nicknamed the "hockey stick," produced by climatologist Michael Mann, in its Third Assessment Report. The graph clearly shows the effects of human activity on climate change, with a spike upwards around the advent of the Industrial Revolution, when humanity's carbon dioxide emissions began in earnest. This graph is a dramatic representation of humankind's interference with nature and appears to be irrefutable proof of anthropogenic climate change.

But skeptics investigating Mann's methods believe that he had misused some data, specifically data from tree rings which indicated a response to carbon dioxide rather than temperature, to make his graph show the results he wanted. Mann vehemently defends his methodology.

Regardless of who or what is to blame, if anthropogenic climate change skeptics believe in global warming, then where's the rub? Read on to find out about what's at stake in the debate over climate change.

Mitigation and Adaptation

Water resources are already scarce in some regions (like Somalia, shown above), and the IPCC warns that under global warming water resources will only become more strained.

In its Fourth Assessment Report (AR4), the Intergovernmental Panel on Climate Change warns of the dire future the Earth will face if global warming continues at the predicted rate. As many as 70 percent of extant species may become extinct if temperatures increase by more than 3 degrees Celsius per year. Millions of people may die from floods, droughts, blizzards and other weird weather patterns. Currently arable land will become arid desert, and water resources will become strained.

To combat these dire consequences, the IPCC advises people to take a two-pronged approach toward dealing with global warming: mitigation and adaptation. Rather than serving as a uniting force -- a rallying point for believers in climate change to meet -- this approach created a schism between climate change factions.

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Mitigation supposes that people can have an impact on reversing climate change. It also implies that human activity is at least in part responsible for global warming. Anthropogenic skeptics find this claim to be false and opt instead to support adaptation measures.

Adaptation efforts aim to help humanity thrive as a species under the future conditions of climate change. These include relocating settlements in areas projected to become arid land or under water in the next century. Or encouraging the reuse of gray water. Or learning how to farm on mountaintops, where much of the precipitation is projected to occur by 2100. Or keeping an eye on diseases which thrive in hotter climes, like malaria.

Anthropogenic warming skeptics believe adaptation is the key to surviving what they consider an irreversible tide. They believe mitigation, on the other hand, could spell disaster. If enforced, they say, mitigation could actually prevent adaptation.

Mitigation relies on regulation. The IPCC's mitigation measures include, first and foremost, a reduction in the emission of carbon dioxide. Skeptics claim that government-mandated reductions could damage economies by forcing developing countries to utilize expensive alternatives to fossil fuels for their budding industries. If regulations are enforced, and if mitigation isn't enough, these nations won't have the finances to fund adaptation procedures when they're most needed.

Skeptics also criticize the effects biofuel could have on the global food supply. Arable land is valuable throughout the world, and if farmers opt to grow switchgrass for use in ethanol fuel production, food supplies could become strained as prices rose. And those in developing countries eating grain-based diets wouldn't be the only ones to suffer. Livestock requires grain, and an increase in grain prices could also lead to reductions in meat production, affecting richer countries as well.

Then again, livestock requires water -- about 1,000 times more per ton than it takes to produce a ton of grain. So if future climate change reduces global water supply, people won't have livestock anyway. Not to mention the myriad other problems that will come along with global warming, if the IPCC is correct.

And here we reach the reason for the urgency -- and the passion -- behind the arguments on both sides of the climate change debate. Inaction risks future catastrophe. Hasty action may cause present calamity.

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